Definitely Sans and Papyrus from Undertale paired with their Underswap counterparts. The contrast between the more laid - back or goofy Underswap Sans and the regular Sans, and also between the more timid Underswap Papyrus and the enthusiastic Papyrus from Undertale makes for great storytelling. Fans also enjoy seeing how they react to each other's worldviews and habits. And then there's also the pairing of Toriel from Undertale and her Underswap version, especially when it comes to exploring their motherly natures in different settings.
Sans from Undertale and his Underswap counterpart are often a popular pairing. People like to explore how the two different versions of him interact, given their different personalities. Another popular one is Papyrus from Undertale and his Underswap version. They can have some really funny exchanges.
Frisk is also quite popular. Their role as the main character in Undertale and how they would interact with the darker or different versions of characters in Underfell and the swapped - up world of Underswap makes for great fanfiction material. They can be the mediator or the catalyst for change in the crossover story.
Susie and Undyne would be a great pair. Susie is the tough - looking monster from Deltarune, and Undyne is the powerful fish - like monster in Undertale. They could have an epic battle at first, but then realize they have a lot in common. They both have a strong sense of justice and a love for fighting. After their initial clash, they could team up to fight a greater evil, perhaps something that threatens both Deltarune and Undertale. They could exchange fighting techniques and learn from each other's strengths.
Naruto and Sans are quite a popular pairing. Naruto's energetic and determined nature contrasts with Sans' laid - back and somewhat mysterious attitude, making for an interesting dynamic. They could bond over their shared experiences of protecting their respective worlds.
Ruby and Sans are quite popular. Ruby's energetic and positive personality contrasts well with Sans' lazy - yet - deep - thinking nature. Their interactions can be really interesting as they come from such different worlds but share a certain sense of humor. Another popular pairing is Weiss and Papyrus. Weiss' elegance and determination can play off Papyrus' over - the - top confidence and his own sense of honor in a really engaging way.
Naruto and Ichigo are often a popular pairing. They are the main protagonists of their respective series and fans like to imagine how they would interact. Their different yet powerful abilities make for an exciting combination.
It's a fan - made concept where the worlds or characters of Underswap and Undertale interact. It often features unique storylines that combine the different character traits and settings from both.
Underswap Chara could develop a sense of respect for Sans. Sans is known for his power and intelligence in the Undertale world. Through their interactions, Chara might see that there are different ways of handling situations than what they're used to in their own world. They could learn from Sans' more laid - back approach and start to adopt some of his non -chalant attitude towards things. This could lead to a more mellow version of Chara in the fanfiction.
Chara is often a popular character. Their complex nature makes them interesting to explore in the context of Storyshift. They can be portrayed in different ways, sometimes more sympathetic than in the original Undertale.
Twilight Sparkle from MLP is often a popular choice. Her intelligence and powerful magic make her a great character to interact with the complex world of Undertale. In Undertale characters, Sans is also quite popular in these crossovers. His laid - back but mysterious nature can create interesting dynamics when paired with the ponies.
Sans is often a very popular character in these fanfictions. In both Undertale and Underfell, he has a distinct personality. In Underfell, his more edgy and somewhat darker side can create interesting interactions when combined with the regular Undertale Sans.